[UVM basics] TLM common data receiving and sending and data receiving examples

stay UVM in , Usually use TLM（ Transaction Level Modeling） Realization component Between transaction Level communication .

This section will cover the following figures UVM Take the tree structure as an example , demonstration UVM transaction Data receiving and sending of level communication （uvm_analysis_port） And data reception （uvm_blocking_get_port）.

The flow of data is ：my_model It's from my_agent Of my_monitor Get in my_transaction, After treatment ,my_model hold my_transaction Pass to my_scoreboard.

1、 Data receiving and sending （uvm_analysis_port）

stay UVM Of transaction Level of communication , There are many ways to send data , One is the use of uvm_analysis_port. stay my_monitor The following variables are defined in ：

 file ： src/ch2/section2.3/2.3.5/my_monitor.sv
uvm_analysis_port #(my_transaction)  ap;

uvm_analysis_port Is a parameterized class , The parameter is this analysis_port The type of data to be transferred , In this section is my_transaction.

The statement ap after , Need to be in monitor Of build_phase Instantiate it ：

 file ： src/ch2/section2.3/2.3.5/my_monitor.sv
   virtual function void build_phase(uvm_phase phase);
      super.build_phase(phase);
	  ...
      ap = new("ap", this);
   endfunction

stay main_phase in , When you finish collecting one transaction after , It needs to be written to ap in ：

task my_monitor::main_phase(uvm_phase phase);
	my_transaction tr;
	while(1) begin
		tr = new("tr");
		collect_one_pkt(tr);
		ap.write(tr); // write in ap
	end
endtask

write yes uvm_analysis_port A built-in function of . Here we are , stay my_monitor We need to provide for transaction The communication preparation has been completed .

2、 Data reception （uvm_blocking_get_port）

UVM Of transaction There are also many data receiving methods for level communication , One of them is to use uvm_blocking_get_port. This is also a parameterized class , Its parameters are to be passed in transaction The type of .

stay my_model in , Defines a port

uvm_blocking_get_port #(my_transaction)  port;

And in build_phase Instantiate it in ：

function void my_model::build_phase(uvm_phase phase);
   super.build_phase(phase);
   port = new("port", this);
endfunction

stay main_phase in , adopt port.get Task to get from i_agt Of monitor It's coming out of transaction.

task my_model::main_phase(uvm_phase phase);
   my_transaction tr;
   my_transaction new_tr;
   super.main_phase(phase);
   while(1) begin
      port.get(tr); // Receive from monitor Of transaction
      ...
   end
endtask

3、 Connect send and receive ports

stay my_monitor and my_model After each port is defined and implemented in , The function of communication has not been realized , Still need to be in my_env Use in fifo Connect the two ports together . stay my_env Define a fifo, And in build_phase Instantiate it ：

 file ： src/ch2/section2.3/2.3.5/my_env.sv
class my_env extends uvm_env;
   ...
   uvm_tlm_analysis_fifo #(my_transaction) agt_mdl_fifo;
   
   virtual function void build_phase(uvm_phase phase);
      super.build_phase(phase);
	  ...
      agt_mdl_fifo = new("agt_mdl_fifo", this);
   endfunction
   ...
endclass

fifo The type is uvm_tlm_analysis_fifo, It is also a parameterized class itself , Its parameters are stored in transaction The type of , Here is my_transaction.

after , stay connect_phase Lieutenant general fifo Respectively with my_monitor Medium analysis_port and my_model Medium blocking_get_port Connected to a ：

 file ： src/ch2/section2.3/2.3.5/my_env.sv
function void my_env::connect_phase(uvm_phase phase);
   super.connect_phase(phase);
   i_agt.ap.connect(agt_mdl_fifo.analysis_export);
   mdl.port.connect(agt_mdl_fifo.blocking_get_export);
endfunction

Why do we need a fifo Well ？ You can't put my_monitor Medium analysis_port and my_model Medium blocking_get_port Connected ？ because analysis_port Is non blocking , ap.write After the function call is completed, it will return to , Do not wait for data to be received . Suppose that write When a function is called ,blocking_get_port Busy with other things , When you're not ready to receive new data , At this time write Function write my_transaction You need a temporary storage location , This is it. fifo.

In the above connection , Yes i_agt A member variable of ap, Its definition is similar to my_monitor in ap The definition of is exactly the same ：

 file ： src/ch2/section2.3/2.3.5/my_agent.sv
uvm_analysis_port #(my_transaction)  ap;

And my_monitor Medium ap The difference is , No need. my_agent Medium ap instantiate , And just need to be in my_agent Of connect_phase Lieutenant general monitor The value of , let me put it another way , This is equivalent to a point my_monitor Of ap The pointer to ：

 file ： src/ch2/section2.3/2.3.5/my_agent.sv
function void my_agent::connect_phase(uvm_phase phase);
   super.connect_phase(phase);
   ap = mon.ap;
endfunction

According to the introduction connect_phase Execution order of , my_agent Of connect_phase The execution order of is earlier than my_env Of connect_phase Execution order of , So as to ensure the execution to i_agt.ap.connect When the sentence is , i_agt.ap Not a null pointer .